With the popularity and continuing development of devices such as cellular phones in recent years, higher capacities are being desired for batteries that are used as their power sources. Of particular note are metal-air batteries, as high-capacity batteries that are superior to the currently widely used lithium ion batteries, since an oxidation-reduction reaction of oxygen is performed at an air electrode by utilizing the oxygen in the air as an active material for the air electrode, and an oxidation-reduction reaction of a metal constituting a negative electrode is performed at the negative electrode, so that charging and discharging are possible respectively allowing high energy density (NPL 1).
For higher capacity in a metal-air battery, there has been proposed an air battery comprising a positive electrode that is a positive electrode layer molded into a sheet as the positive electrode of the metal-air battery, and composed mainly of a carbonaceous substance with pores of 1 nm and larger (PTL 1).